In the course of refining petroleum to produce products such as, for example, fuel, lubricants, and petrochemical compounds, various intermediate and byproduct feedstreams are created. Some of these feedstreams are highly concentrated in C8 hydrocarbons, and some feedstreams, in particular, contain styrene and/or ethylbenzene. Ethylbenzene can be produced by hydrogenation of styrene, and dehydrogenation of ethylbenzene correspondingly produces styrene. Because of its tendency to dimerize and polymerize, styrene is considered to be an unwanted component in feedstreams ultimately intended for fuel use as gasoline. However, styrene is an economically important commodity chemical used in a number of commercial applications such as, for example, as a starting material for making polystyrene. As there is a growing demand for polystyrene-type products, there is accordingly a growing need for styrene raw material.
In view of the foregoing, new methods and systems for separating styrene from a styrene-containing feedstream would be of substantial benefit in the art. In particular, efficient methods and systems to maintain extractive solvent performance in the extractive distillation of styrene from other materials found in pyrolysis gasoline streams would be of specific benefit.